1. Field of the Invention
This invention relates to the process of integrally forming one-piece roadway markers with multi angled sides having designated impact regions to minimized vehicle impact, which are used as traffic lane divider retro-reflecting light from oncoming vehicles, thereby delineate the roadway to the driver.
2. Related Art
Roadway markers are adhered to pavements along centerlines, edge lines, lane dividers or guardrail delineators.
Since 1965, the most commonly used retroreflective roadway markers are based on Heenan U.S. Pat. No. 3,332,327 and Balint U.S. Pat. No. 3,409,344.
Typically, these types of markers are produced in a process consisting of three to four steps:
Firstly, injection molding of a thermoplastic shell, either integrally molded with the reflective face, or the reflective faces welded on a corresponding open recesses within the shell.
Secondly, either the reflective faces within a shell or the entire inside surface of the shell coated with a reflective metallic sealer by a process known as vacuum metalizing.
This metallic sealer needed firstly to protect the cube corner reflective elements and to retain part of retro-reflection after filling the shell with a thermosetting resinous material, such as inert filled epoxy or polyurethane resin.
This resinous filler material encapsulate the metalized cube corner reflective elements and form the marker's structural body. Finally, a layer of relatively course sand or glass beads dispersed over the top surface of the filler material prior to solidification of the filler material. Part of the sand particles will remain partially protruding above the planar base surface of the marker, thereby increase the adhesive welding parameter of the base surface. The protruded sand will improve adhesion to substrate, regardless of the type of adhesive used. This type of markers worked well for six or seven months, however, due to poor abrasion and impact resistant of the thermoplastic shell, over 60% of the reflectivity lost thereafter. Also, incompatibility of the shell material to the resinous filler material causes pealing of the reflective face or the shell, thereby losing retroreflectivity.
Several attempts were made to improve abrasion resistant of the reflective face. One was the use of thin layer of untempered glass as disclosed in U.S. Pat. No. 4,340,319, another attempt was the use of polymeric coating of the reflective face, as disclosed in U.S. Pat. No. 4,753,548 to (Forrer). These abrasion resistant coating proving to be expensive and tend to reduce retro reflectivity. Other major development in the pavement marker art has been made, this was achieved by eliminate the use of the metalized sealer for the cube corner reflective elements. U.S. Pat. No. 4,227,772 (Heenan); U.S. Pat. Nos. 4,232,979; and 4,340,319 (Johnson et al) disclosed pavement markers having non-metalized reflective faces. This was achieved by dividing the inside surface of the reflective face into reflective cells, with each cell retaining several cube corner reflective elements. The cells are isolated from each other by partition and load carrying walls. The reflective face is welded to a correspondingly recessed face within a hollowed structural body, thereby retaining the reflective prisms in an air space. These markers proved to be superior in reflectivity, however, they lacked structural strength and showed poor adhesion to the roadways, causing short life cycle and in some regions had the tendency to shift location on the roadways. This applicant successfully developed a one-piece reflective roadway marker, which is a monolithically injection molded reflective pavement marker including a reflective prismatic face, structural body and a hollowed base that is sealed with a compatible plastic sheeting. This one-piece marker was disclosed in this Applicant's U.S. Pat. Nos. 6,334,734 and 6,698,972. The '734 and '972 patents disclosed one-piece reflective markers that proved to have better structural stability and consistently the same retro-reflective value, due to being homogeneously injection molded under a very high pressure and from one type of moderate to high impact resistant polymer.
However, there is no recognition apparent from the '734 and '972 patents that there is a need for designating lower impact regions within the marker inclined sides. The '734 and '972 did not recognize the need for providing the designated marker's side grip regions with angular surface equal to the angle formed by the centerline of each hollow cavity defining the interior structural walls, which eliminate the usage of the costly process of using slides for the injection molding tooling.
Also the '734 and '972 patents did not recognize that the base sealer sheet need to be injection molded having a thickness of at least about 0.07 to 0.10 inch, with textured and grooved outer surface as well as an inside surface with energy directors and at least two guiding pins for improved sonic welding and providing such sealer sheet with definitive periphery geometric shape to avoid wasted welding time.
It has been discovered that a reflective pavement marker with two reflective faces can be formed by injection molding only a half marker monolithically including one reflective face, interior structural walls, at least two tong and groove means with energy directors and at least one guiding pin means. Two half markers are then attached to each other through the guiding pin means, thereby firmly aligning the tong and groove slots to be sonically welded.
It has also been discovered that a double sized reflective pavement marker can be formed utilizing the process of the present invention. Such double sized reflective markers are favorably needed for use in the double stripping portions of Freeways and roadways, such as the entrance or exit lanes and other commonly known as the Y intersections junctions of two splitting roadways.
This application also provides the means for an improved reflective face with maximum retro-reflective cells and a streamlined body for smoother and reduced vehicular impact.
Also it is the desire of this application to have an improved method for abrasion resistant coating the outer marker body, inclusive the reflective face. This can be achieved economically by spraying the entire outside surface of the marker with coating composition such as the teaching of U.S. Pat. No. 4,486,504 assigned to General Electric Company which utilizes acrylates with functional silanes or the teaching of U.S. Pat. No. 5,126,394 and U.S. Pat. No. 5,648,173 assigned to Dow Corning corporation which provide a room temperature, moisture curable abrasion resistant coating compositions having multifunctional acrylate.